Effects of chronic decaffeinated green tea extract supplementation on lipolysis and substrate utilization during upper body exercise

Abstract

Background Decaffeinated green tea extract (dGTE) can increase fat oxidation during leg exercise, but dGTE is unsuitable for many people (e.g., those with injuries/disabilities), and its effects on arm exercise and women are unknown. Methods Eight adults (23–37 years old, 4 women) performed an incremental arm cycle test to measure peak oxygen uptake (VO2peak), followed by four 1-h trials at 50% VO2peak. Subjects were randomly assigned to 650 mg of dGTE or placebo (PLA) for 4 weeks followed by a 4-week washout and crossover trial. Blood samples were obtained pre-exercise and post-exercise for glycerol and free fatty acid analysis. Respiratory gases were collected continuously. Results VO2 showed no differences across trials ((0.83–0.89) ± (0.19–0.25) L/min, p\u202f=\u202f0.460), neither did energy expenditure ((264–266) ± (59–77) kcal, p\u202f=\u202f0.420) nor fat oxidation (dGTE\u202f=\u202f0.11 to 0.12 g/min vs. PLA\u202f=\u202f0.10 to 0.09 g/min, p\u202f=\u202f0.220). Fat oxidation as percentage of energy expenditure was not different for dGTE vs. PLA (23% ± 12% to 25% ± 11% vs. 23% ± 10% to 21% ± 9%, p\u202f=\u202f0.532). Glycerol concentration increased post-exercise in all trials, independent of treatments (pre\u202f=\u202f(3.4–5.1) ± (0.6–2.6) mg/dL vs. post\u202f=\u202f(7.9–9.8) ± (2.6–3.7) mg/dL, p\u202f=\u202f0.867, η2\u202f=\u202f0.005 for interaction), as did free fatty acid ((3.5–4.8) ± (1.4–2.2) mg/dL vs. (7.2–9.1) ± (2.6–4.5) mg/dL, p\u202f=\u202f0.981, η2\u202f=\u202f0.000). Conclusion Chronic dGTE supplementation had no effect on lipolysis and fat oxidation during arm cycle exercise in men and women.